This study proposes to identify factors influencing decision-making regarding genetic testing for Hereditary Nonpolyposis Colorectal Cancer (HNPCC) and the psychological and behavioral outcomes of the testing process. Those with a cancer meeting selection criteria or in a family with a known HNPCC mutation complete a baseline questionnaire assessing knowledge, expectations, mood, attitudes, perceived cancer risk, cancer worries, family relationships, spirituality, coping and health beliefs. Participants are then provided with an educational/counseling session focused on HNPCC, the availability of genetic testing, its risks, limitations and potential benefits, and cancer screening recommendations for families with HNPCC. Participants are then presented with a choice of whether or not to undergo genetic testing. Those choosing genetic testing undergo a separate informed consent specifically focused on the process of genetic testing and the potential risks, benefits and limitations of genetic testing. Psychological and behavioral outcomes are reassessed through telephone questionnaire at 6 and 12 months following risk notification or the decision not to undergo testing. For those receiving genetic test results, notification occurs in person along with discussion of available surveillance options. Follow-up counseling and support are provided for all individuals participating in the study. First degree adult relatives of individuals with identified HNPCC germline mutations are also offered participation in the study. To date, 275 individuals have completed baseline questionnaires, 165 individuals have completed 6- month follow-up questionnaires, and 133 have completed 12-month questionnaires and are currently off study. In the process of offering testing to this population, we have collected a growing number who do not have mutations identified however clearly have inherited forms of colon cancer. This finding is leading us to develop a protocol which explores the impact of inconclusive results on family communciation and cancer screening practices.